Process control systems, like those used in chemical, petroleum or other processes, typically include one or more process controllers and input/output (I/O) devices communicatively coupled to at least one host or operator workstation and to one or more field devices via analog, digital or combined analog/digital buses. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure and flow rate sensors), perform process control functions within the process such as opening or closing valves and measuring process control parameters. The process controllers receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices, use this information to implement a process control routine and/or control strategy, and then generate control signals that are sent over the buses or other communication lines to the field devices to control the operation of the process. In this manner, the process controllers may execute and coordinate control strategies using the field devices via the buses and/or other communication links communicatively coupling the field devices.
Information from the field devices and the controllers may be made available to one or more applications (i.e., software routines, programs, etc.) executed by the operator workstation (e.g., a processor-based system) to enable an operator to perform desired functions with respect to the process, such as viewing the current state of the process (e.g., via a graphical user interface), evaluating the process, modifying the operation of the process, etc. Many process control systems also include one or more application stations. Typically, these application stations are implemented using a personal computer, workstation, or the like that is communicatively coupled to the controllers, operator workstations, and other systems within the process control system via a local area network (LAN). Each application station may execute one or more software applications that perform campaign management functions, maintenance management functions, virtual control functions, diagnostic functions, real-time monitoring functions, safety-related functions, configuration functions, etc. within the process control system.
Process control engineers create process control diagrams and/or graphics to display important process control information to system operators. This process control information may take the form of a piping and instrumentation diagram (P&ID) that shows the interconnection of process equipment and the instrumentation used to control the process, along with a logical representation of a control strategy for the process.